For example, a pressurized water reactor (PWR) uses light water as a reactor coolant and a neutron moderator, fills an entire reactor core with not-boiled, high-temperature and high-pressure water, transfers the high-temperature and high-pressure water to a steam generator to generate steam by heat exchange, and transfers the steam to a turbine generator to generate power. Further, the pressurized water reactor transfers heat of high-temperature and high-pressure primary cooling water to secondary cooling water by a steam generator, and generates water vapor with the secondary cooling water. The steam generator has the primary cooling water flowing inside a plurality of narrow transfer tubes, and transfers the heat to the secondary cooling water flowing outside to generate the water vapor, and rotates a turbine with the water vapor to generate power.
In the steam generator, a tube bundle shroud is disposed in a trunk body having a hollow sealed shape with a predetermined interval with an inner wall surface of the trunk body, a plurality of inversely U-shaped heat transfer tubes is disposed in the tube bundle shroud, an end portion of each of the heat transfer tubes is supported by a tube plate, and an inlet-side channel head and an outlet-side channel head of the primary cooling water is formed in a lower end portion of the trunk body. Further, the trunk body is provided with an inlet portion of the secondary cooling water positioned above the tube bundle shroud, the steam-water separator and the moisture separator aligned and disposed up and down, and a steam outlet above the steam-water separator and the moisture separator.
Therefore, the primary cooling water is supplied to the plurality of heat transfer tubes through the inlet-side channel head from a cooling water pipe, while the secondary cooling water is supplied from the inlet portion to the trunk body. Heat exchange is then performed between the primary cooling water (hot water) flowing in the plurality of heat transfer tubes and the secondary cooling water (cool water) circulating in the trunk body, so that the secondary cooling water absorbs heat and water vapor is generated. Water in the generated steam is then removed by the steam-water separator, and the steam from which moisture is removed by the moisture separator is discharged from the steam outlet, while the primary cooling water after completion of the heat exchange is discharged from the outlet-side channel head.
In such a steam generator, the plurality of heat transfer tubes provided in the trunk body is supported by a plurality of tube support plates and a tube plate. The plurality of heat transfer tubes is supported not to vibrate by being inserted into a plurality of holes formed in the tube support plates. In this case, the holes in the tube support plates do not have a circular shape but have a particular shape to form a gap through which steam is distributed between the holes and the heat transfer tubes held by the holes, and are typically machined by a broaching machine. Such a broaching machine is, for example, one disclosed in Patent Literature 1 described below.